Continuous reading electronic micrometer



G. E. CHILTON Erm. 2,850,645

CONTINUOUSi'READING ELECTRONIC MICROMETER Sept. 2, 1958 Filed Feb. 16, 1954 INVENTORS GEURGE E CHILTON RALPH E. WEST BY ArroRNEY United States Patent CQNTINUUS READING ELECTRONIC MICROMETER George E. Chilton and Ralph E. West, Emporium, Pa., assignors to Sylvania Electric Products luc., a corpo ration of Massachusetts Application February 16, 1954, Serial No. 410,551

Claims. (Cl. Z50-232) The invention relates to electronic measurements of the occlusion of an energy beam by an article which is passing through the beam whether it be because of different densities of different portions of the article or because of different transverse dimensions therealong.

ln particular it relates to the continuous measurement of the diameter of an object, such as a wire or a cathode sleeve, passing through a light beam.

ln a practical application of the invention the running diameter of a wire or a cathode is measured by passing the same in the direction of its longitudinal axis in front of an illuminated slit and comparing the amount of light transmitted from the slit past the object and impinging on a photocell with the amount of light on the same photocell from the same source passing through another or standard unobstructed slit. To obtain this comparison, a shutter revolves in front of the two slits to gate the beam so that alternately the photocell responds to the light from the obstructed slit and to the light from the standard unobstructed slit. By observing a meter or recording instrument the difference in light intensities as continuously translated by the novel circuit arrangement of our invention, can be observed and this observation can be translated into diameters of the object.

It is an object of the invention to provide novel means which shall be sensitive to light variations due to varying diameters of the object being measured.

It is a further object to provide a novel circuit which shall make known the variation in light transmission of an object as it traverses an energy beam.

It is a still further object to provide a novel means for synchronizing the gating of the beams of light through the two slits with the operation of pulse separating means in the measuring instrument.

It is yet another object of the invention to provide electronic means to maintain at a constant magnitude the electrical representation of the gated beam of light passing through the standard slit.

Yet another object is to obtain this constant magnitude by automatically varying the voltage on the photocell to compensate for undesired changes taking place in the apparatus.

These and other objects will become apparent after reading the following specification and claims when taken in conjunction with the accompanying drawing in which the gure diagrammatically discloses the diameter sensing mechanism and the circuit associated therewith to give a continuous indication of the light transmission of an object passing by one of a pair of slits.

Referring to the drawing in greater detail, there is represented at l@ a window frame having two parallel openings 12 and 14, forming slits through which pass beams of light, These beams originate at a single point source 16, the light from that source being collimated by a lens 17 and then reaching the slits via openings in a revolving shutter 18. The beams from the slits are focused by a condensing lens 20 so that the image of the light source rather than the image of the window slits falls on the photo cathode of a conventional multiplier phototube 22 said tube being a light to electric energy transducer. Passed in front of one of the slits, either perpendicular to the long axis of the slit or parallel to the said axis, dependent on whether greater sensitivity of the system or greater resolution is sought, is the article whose light transmission characteristic is to be measured.

ln the diagram, the object passed in front of a slit is shown as a wire 24 and that slit is additionally provided with a blade 26 movable to adjust the width of the slit so that substantially as much light passes through the slit when the wire is juxtaposed thereto as lthrough the lower unobstructed slit, which latter may be regarded as the standard. The blade may be adjusted by any convenient means, as a thumb screw 28.

The shutter 1S is provided with a pair of arcuate slots 3G at such a radial distance from the center of rotation of the shutter as to permit light to pass through the slit 12. The shutter is further provided in this specific example with a second pair of slots 32 nearer the center of the shutter and out of phase with the rst pair of slots to permit light to pass through the slit 14 in alternation with the light passing through slit 12. Of course the slits 12 and 14 are suitably spaced apart and located to register with the slots in the rotating shutter. The shutter is direct driven by a motor 34, connected into the A. C. power line, which for example, may be a conventional 60 cycle, 117 volt supply line. The drive between tne motor and the shutter is in a 1 to l ratio. For diagrammatic convenience the drive is shown as a straight shaft connecting the motor and the shutter, but in actual practice geared or exible shafting may be employed. It is desirable, for greatest resolution of the diameter of the wire to revolve the motor at high speed. At 60 C. P. S. the highest synchronous motor speed is 3600 R. P. M., and the motor must be of the type wherein its rotor is always xedly phase in either one of two positions with respect to the phase of the power line voltage. There are two pairs of openings in the shutter resulting in two pairs of electrical pulses being generated in the measuring instrument for every revolution of the motor and the shutter. This requires gating pulses twice the line frequency of C. P. S. to permit proper subsequent separation of the pulses. This separation is effected by apparatus soon to be described.

The measuring device includes a supply line having suitable transformers to feed the heaters of the various tubes in the circuit and also a power transformer 4t) in the high voltage secondary of which is a full wave rectifier 42, the anodes of which are connected to the ends of the high voltage winding of the transformer secondary and the cathodes of which are connected to the midpoint of the transformer secondary via a primary winding of a transformer 44 and a current limiting resistor e6. The secondary of this second transformer is center tapped and grounded, as at 48. The 120 cycle pulsating D.-C. in the primary is converted in the secondary into a 120 cycle A.C. This provides the 120 cycles alternating current previously pointed out as being necessary for proper functioning of the pulse dierentiator or pulse separator. The secondary of transformer 44 may be tuned to the 120 cycle current so as to discriminate against higher frequencies.

lt is required that the sensitivity of the photocell or the photocell-ampliiier combination be controlled so as to maintain at a fixed known amplitude, as measured at the comparison stage, the pulses corresponding to the light passing the unobstructed slit. This control will be accomplished by means soon to be described.

The pulsating signal from the multiplier phototube 22 is fed via condenser 78 and resistor 80 to the grid of a phase inverter triode 82. Some of the output signal from Vdifferently Vby each .of the `halves of the duo-triode.

the inverter 82 is fed back to the grid via condenser 83 and resistor 84 to reduce the overall gain of the stage and to provide the inherent stabilityof a negative feedback amplifier. Gain is not necessary in this stage as itsprimary Vfunctionis to invert..the Voutputfrorn the' multiplier` phototube. The output v'from theV phase inverter isfed to a cathode follouV/erft.v The cathode. follower.` is-used toV permit the .remainder ofthe circuit .tol

befremotely located without loss of signal in the connect-V ing.v cables. From. the-cathode follower, thepulses are fed via lead 8810 the anodesbf a pulse separator stage, comprising duo-triodet), whose grids: are controlledby the 1Z0-cycle alternating current produced as previously described. The pulses fromrthe phototube,l while appearingat both .anodes of the..duo`-triodei90, Yare treated lf, forfexarnple, the grid 92 be in `positive phase, the signal atVV the corresponding'anod'e 93, Ywhich should correspond to the measuring signal, Vwould be shunted to ground. 'Since the other grid 94.is'l80 out-of-phase, the measuring signal at its corresponding anode 95 is not so shuntedfto ground. The resistors 96 form a dividing network to preventfthe entire signal appearing on line 88. from being shunted out. Since the Vgating of the duo-triode is synchronized withY shutter rotation,'the voltages appearing at the anodes 93 and 95 will correspond to the amount of light passing through the VrespectiveV slits 12 and 14. The non-grounded out measuring voltagerappearing at the anode 95 isnapplied'to the grid l98 of a comparator'duo-triode 10), while the non-grounded Vout standard voltage appearing at the'anode 93 is applied to the grid 102 of the same duo-triode. The two portions of the duo-triode Vare cathode connected to groundvia resistors 104, and each of the .resistors is i It shouldbe noted that Vthe D.C. value appearing on the line 112 (connected to Vline 110) and which is the average of-the peak values of the standard pulses is usedfto control lthe sensitivity of the multiplier phototube, so that in'spite ofv changes in line voltage, aging of light sourceychanges in photocell sensitivity,'etc., the D.C. valueappearing on the line 112 will have a value which is essentially under control at all times of a reference voltage obtained'from Vseriesconnected .VR tubes 54 and 56 and current limitingresistor 58. This reference potential is obtained from the center arm of a potentiometer V69, which is used so that the reference voltage l VVcan be adjusted to a Ysuitable value.

The D.C. value appearing on line 112 is Vfed back through the smoothing resistor 114 to the grid of triode 62 The grid of tube 62 is also Vcontrolled via Ycondenser 72by the ripple component of D.C..voltage appearing at the cathode of tetrode 52..V YThe referenceV potential from the center armcf potentiometer 6i) is Ysupplied to the cathode of triode 62. A potential whichpis a function of the difference betweenthe grid and the cathode volt-V age of triode 62 appears at they plate of triode 62. This plate is connected Vto the rectier via ya resistor 64.vr YThe plate in turn is directly Vconnected to the grid of regulator.

. tubeV 52 controlling the impedance of tetrode S2 and thereby exercisescontrol Von vthe voltage appearing at the cathode of tetrode 52. The voltage applied to theV plate of tetrode 52 and tothe screen grid via plate load resistor Y53 is obtained'from -a half Vwave rectier circuit comprised of the high voltage winding of Vtransformer 4t),

tubes in the circuit through provision of the ground return at 76. As theamplification of the multiplier phototube is exponentially proportional to the applied D.C. potential, overall gain control over ya Wide range is thus achieved. Y

We have thus provided an instrument which, notwithstanding -changes in intensityl'of .the light source or changes in the instrumentdueto aging of components, will give accurate indications of the transmission characteristics of an object traversing theV measuring slit.

What is claimed as new is:

1. In a measuring instrument, means providingl a source of light, a window having two slits through which beams of light from saidV source pass,r a synchronous motorv driven at maximumA speed at line frequency, a shutter driven in l to 1 ratio from said motorand having plural pairs of slots for gating said beams through thetwo slits, means for causing the gated Vbeams of light to impinge on atransduceLto. convert Vthe energy ofthe gatedV lightv beams.into..-electricalgpulses, means forfeeding `the train.of;pulses.comprised.of.alternate pulses correspondingwith the alternate gatingof the two beams of light to-an electronic two.. part separator in order to separate the two setsvof'pulses linto twoV trains each corgating each partof said separator.V at frequencyA equal to half the frequency ofV light impingement on the trans'- responding to itsV respective Ybeam of Vlight, means for.

.ducer, means under control of vsaid two separated trains of pulses Afor setting up continuous but averaged elec.

trical potentials proportional `to theV magnitude of the pulses -with averagedL potentials.. in opposition to one` another, Wherebycontinuous exhibitingof Ythe resultant, .potential may be obtained 2. In a measur-ing instrument,` means providing aV source-oflight, a window Yhaving' twol slits throughwhich beams of light from said source pass, a synchronous motoradapted toY beconnected--to anrAfC. lineaind'` rotating at-` .Va speedequal tov the-linefrequency, a shutter. connected to the motor and driven at motor speed, said shutter:

havinga pair ofA-slots-circumferentially spaced, a second circumferentially-spaced pair of yslots in said shutter, saidy tirst-pair5ofslotsgating the light through oneslit, said secondrpair" ofslots'gating `the lightthrough the second slit', means for` causing the1gated beams toimpinge on f a transducer tonconvert theenergy of the `gated beams of light into; electric .pulses,lmeans for .feedingA thek train of pulses comprised of pulses-resulting from the-alternate A gating of thetwo beams of lightin alternation to a pair of Y grid controlled tubes, eachofsaid tubesV also havingV an y reetitiertube Stlandiilter condenser 66. This controlled Y voltage is. applied via line 74 to the multiplier phototubre'22. .Y A lesserfvoltage is appliedV totheremaining ,Y

' separator in order to Vseparaterthe two .sets 'of pulses intoV f two trainsgeach correspondingto its respective AVbeam ofi-` anode and a'groundedY cathode,-a full waveV rectifier adapted to be connectedA tothe same A.C. line, said rectiiier having a portion of its circuitcarrying a ripple com? kponent at twice line lfrequency',` a Vtransformer inv said portion of the circuit, thesecondary of said transformer being grounded substantially at its midpoint, means connecting the ends of the secondary with the grids of the tubesfmeansfor feeding eachrof the pulses to theV anodes of both tubesA to thereby separate said trainof pulses into two .trains of pulsesfeach corresponding to its respective beam of light, means under control of said two Y separated trains vofpulses for setting upcontinuous electrical potentials proportional lto thel magnitude of the i ing thegated beams of light. to Vimpinge onV a transducer Y to convert` the energy` of thegatedV lightl beams into electrical pulses, means for feeding the train of pulses comprised of alternatepulses vcorresponding Vwith the alternate gating of the' two beams of light to an electronic light, means under control of said two separated trains of pulses for setting up continuous but averaged electrical potentials proportional to the magnitude of the pulses, with the averaged potentials in opposition to one another, whereby continuous exhibiting of the resultant potential may be obtained, and means under control of the light passing through one slit to regulate the voltage applied to portions of the measuring instrument.

4. In a measuring instrument, means providing a source of light, a window having two slits through which beams of light from said source pass, means for alternately gating said beams through the two slits, means for causing the gated beams of light to impinge on a multiplier phototube to convert the energy of the gated light beams into electrical pulses, means for feeding the train of pulses comprised of alternate pulses corresponding with the alternate gating of the two beams of light to an electronic separator in order to separate the two sets of pulses into two trains each corresponding to its respective beam of light, means under control of said two separated trains of pulses for setting up continuous but averaged electrical potentials proportional to the magnitude of the pulses, with the averaged potentials in opposition to one another, whereby continuous exhibiting of the resultant potential may be obtained, and means under control of the light passing through one slit to regulate the voltage applied to portions of the measuring instrument including the multiplier phototube.

5. In a measuring instrument, means providing a source of light, a window having two slits through which beams of light from said source pass, means for alternately gating said beams through the two slits, means for causing the gated beams of light to impinge on a transducer to convert the energy of the gated light beams into electrical pulses, said transducer having an energy gain or sensitivity which is a function of an applied voltage, means for feeding the trains of pulses comprised of alternate pulses corresponding with the alternate gating of the two beams of light to an electronic separator in order to separate the two sets of pulses into two trains each corresponding to its respective beam of light, means under control of one separated train of pulses corresponding to one of the beams of light to vary the voltage applied to the transducer in such a manner as to keep at a constant amplitude the pulses in the pulse train exercising this control, means under control of said two separated trains of pulses for setting up continuous but averaged electrical potentials proportional to the amplitudes of both trains of pulses, with the averaged potentials in opposition to one another, whereby continuous exhibiting of the resultant diierence of potentials may be obtained, said diierence of potentials being a linear function of the ratio of the intensities of the two gated Ibeams of light by virtue of the control exercised on the gain of the system in keeping at a constant value the electrical representation of the intensity of one of the gated beams.

References Cited in the le of this patent UNITED STATES PATENTS 2,474,098 Dimmick June 21, 1949 2,548,755 Vossberg et al Apr. l0, 1951 2,583,143 Glick Jan. 22, 1952 2,653,247 Lundahl Sept. 22, 1953 2,678,581 Reisner May 18, 1954 

